\section{数的分类}
real number
rational number
repeating decimal,recurring decimal
finite decimal
integer

finite decimal does not have non-uniqueness representation

fraction ,2,5, infinite

Every repeating or terminating decimal is a rational number。
A fraction in lowest terms(Irreducible fraction) with a prime denominator other than 2 or 5 (i.e. coprime to 10) always produces a repeating decimal. 

